1. Field of the Invention
The present invention relates to an imageable element comprising a substrate and a thermally imageable composition coated on a surface of the substrate. The thermally imageable composition comprises a thermally sensitive polymer, which comprises at least one covalently bonded unit and at least one thermally reversible non-covalently bonded unit, which includes a two or more centered H-bond within each non-covalently bonded unit. More particularly, the present invention relates to a thermally sensitive supramolecular polymer prepared from a hydrocarbyl-substituted isocytosine, a diisocyanate and a polyfunctional material such as phenolic resin, acrylic resin, polyester resin and polyurethane resin.
2. Description of the Prior Art
WO 98/14504 discloses a supramolecular polymer containing monomeric units, which in pairs, form at least 4 H-bridges with one another. The article in J. Org. Chem., 53, 5787-9 (1988) discloses bifunctional compounds that can associate into polymers or oligomers by 2-center H-bond units. Supramolecular polymers based on 3-center H-bond units are disclosed in Macromolecules, 28, 782-83 (1995). None of the above references discloses the use of these polymers in thermal imaging.
EP 969 966 discloses phenolic polymers together with a non-photosensitive solubility inhibitor which provides acceptor sites for H-bonding and EP 985 166 discloses the corresponding methods. The present invention is directed to a supramolecular polymer having non-covalent interactions, such as H-bonding, as an integral part of the polymer structure. The H-bonding in the present invention is not between a H-donor polymer and a solubility inhibitor having H-acceptor sites, but is an integral part of the polymer structure.
WO 99/01795 discloses phenolic polymers, which are modified with groups that provide acceptor sites for H-bonding with other phenolic polymers. The present invention is directed to a supramolecular polymer having non-covalent interactions as an integral part of the polymer structure.
An article by B. J. B. Folmer et al., Advanced Materials, Vol. 12 (No. 12), pages 874-878 (2000), discloses supramolecular polymer materials. The article does not disclose polymers derived from polyfunctional materials, such as, polyfunctional phenolic resin, acrylic resin, polyester resin or polyurethane resin, nor does it disclose the use thereof in thermal imaging.